Core construction



Dec. 1964 w. E. HAlFLEY ETAL 3,159,762

CORE CONSTRUCTION Original Filed Dec. 30, 1958 Inveni'bra- EdwardJSc/mefer ll/zlllzamliffaz'fiey,

j lee (Ila/662 J/QMI xxx; lliMm United States Patent 9 Claims. (Cl.310-217) This application is a division of our copending applicationtitled Core Construction for Electric Machines, Serial No. 783,987,filed December 30, 1958.

The invention rel-ates to the manufacture of laminated cores forelectric machines and more particularly to a novel form of laminatedcore.

It is a primary object of the present invention to provide a novellaminated core that has excellent magnetic characteristics, is tight andrigid, and is relatively inexpensive to manufacture.

Another object is to provide a novel laminated stator core for electricmotors.

Other objects and advantages of the invention will be apparent from thefollowing description taken in conjunction with the accompanyingdrawing, wherein FIG. 1 is an end view of alaminated core embodying thefeatures of the present invention;

FIG. 2 is an enlarged elevational view of a portion of the edge of thecore shown in FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2; and

FIG. 4 is a view similar to FIG. 3 showing a modified form of theinvention.

A core structure for an electrical machine such as a motor usuallycomprises a plurality of laminations held in superimposed face-to-facestacked relation by longitudinally extending banding-strip material. Thelaminations are each provided with one or more generally rectangularslots in their peripheral edges. When the laminations are assembled, theslots are aligned and form one or more grooves. Each groove extends fromone end of the stack to the other, and mounted in each groove is anassociated banding strip which has its opposite ends bent over the endsof the stack of laminations. Each banding strip .is in longitudinaltension between its bent ends and also each banding strip is deformed inits associated groove so that the banding strip is in lateralcompression between the side walls of its associated groove for tightlygripping the laminations.

The present invention provides banding strips of the foregoingcharacter, which have alternating transversely extending depressed areasand ribs. The strip may be deformed in such a manner as to thicken it atits side edges, particularly in the depressed areas, so that it firmlygrips the laminations to hold them in assembled relation.

Apparatus for assembling cores embodying this invention is shown anddescribed in the aforementioned copending application, Serial No.783,987. The apparatus includes structure for holding a stack of corelaminations in aligned face-to-face compressed relation With the slotsin the edges of the laminations forming one or more banding stripreceiving grooves. The apparatus also includes structure for supportinga strip of handing material and for laying the strip in the groove uponrelative movement between the two structures. The last mentionedstructure includes deforming means, such as a serrated roller, adaptedto flatten and deform the strip in the groove into holding engagementwith the laminations. The banding material is preferably supplied to theapparatus as a continuous strip of flat banding stock, and the apparatusalso includes means for preforming the strip, as well as a device forsevering or cutting the assembled strip from the remainder of thebanding material after banding has been accomplished. The cutting deviceprepares the end of the remaining portion of the banding strip for thenext banding operation. Consequently, the apparatus is adapted to carryout each banding operation quickly and automatically and is thus able tomass produce electrical cores of the preferred form, thereby reducingmanufacturing costs.

FIGS. 1, 2 and 3 of the drawing show a stator core for an electricmotor, embodying the features of the present invention. The corecomprises a plurality of l arninations 11 held in superposed stackedrelation, in this instance, by four circumferentially spaced bandingstrips 12. The laminations 11, in this instance, are generally annularidentically shaped sheets of magnetic material. The inner periphery ofeach laminaion is formed in the conventional manner to provide aplurality of circumferentially spaced pole portions, indicated at 13.The pole portions 13 define slots 14 therebetween adapted to accommodatethe stator field windings. The inner ends of the pole portions 13 definea circular opening adapted to accommodate the rotor (not shown) of themotor. The outer periphery of each lamination is generally circular sothat the core formed thereby may be mounted in a circular motor frame(not shown), but is provided with four circumferentially spacedgenerally rectangular slots in the edge of each lamination. Thus, whenthe laminations 11 are stacked in aligned face-to-face relation, asshown, the aligned slots form four banding strip receiving grooves 16which extend the length of the core.

The banding strip receiving grooves are generally rectangular in crosssection and may be deeper in the center than at their side edges. Asshown in FIG. 3, the groove 16 has a flat-bottom wall 17 andperpendicular side walls 18. In FIG. 4, a modified form of banding strip19 is shown, which is mounted in a modified form of groove having anarcuate bottom wall 21 and side walls 22 which are perpendicular to thechord across the arc of the bottom. The advantages of the differentforms shown in FIGS. 3 and 4 will be discussed hereinafter.

Prior to being mounted in their associated grooves, the banding strips12 and 19 are preferably longitudinally corrugated so that they arenarrower than their associated grooves and thus may be readily placed inthe grooves. Upon being placed in these grooves, the banding strips 12are then flattened and deformed in the grooves. Thus, the strip 12 iscompressed tightly against the bottom wall 17, and at longitudinallyspaced areas the metal of the strip is forced laterally to thicken theedge portions of the strip and force it against the side walls 18, sothat the strip is in compression between the side walls. The thickenededges of the strip provide a firm grip on the laminations. In FIG. 2,the depressed areas are shown at 23 and are longitudinally spaced andgenerally concave. Between the depressed areas 23 are laterallyextending ribs or portions 24 that are corrugated longitudinally of thestrip 12, such corrugating remaining from the original corrugation ofthe strip.

The opposite ends of the strips 12 are bent over the opposite endlaminations of the stack, as shown at 26 in FIGS. 1 and 2. The bendingis accomplished when the stack of laminations is compressed. Thus, thestrips 12 are in tension between their bent ends 26 and hold the stackof laminations compressed.

The modified form of banding strip 19 shown in FIG. 4 differs from thestrip 12 in that it is deformed in a groove having the arcuate bottom21. This results in the center portion of the strip 19 being in anover-center relationship. The exposed surface of the strip 19 has thesame general appearance conformation as the strip 12, that is, it hasgenerally concave depressed areas alternating with longitudinallycorrugated ribs. Because of the over-center relation of its centerportion with respect '3 3 to its side or edge portions, and because thestrip is curved and hence has substantially the same areas of contactwith the sides 22 of the groove as in the previous form, the strip 19has an increased holding effect on the stack of laminations.

From the foregoing it is apparent that the present invention provides animproved form of laminated core structure for electrical machinesincluding electric motor. The core is easily assembled, may be of anyreasonable length, is rigid, and has excellent electricalcharacteristics.

We claim:

1. In combination, a stack of laminations superimposed in face-to-facerelation, said stack having a groove across the edges of the respectivelaminations, said groove being generally rectangular in cross section,and an elongated strip of banding material positioned in said groove andhaving ternating transversely extending depressed areas and ribs on thetop surface thereof, the bottom surface of said strip in said areasconforming to and in tight frictional engagement with said bottom wall;and the opposite side edges of said strip in said areas being compressedagainst said side walls.

2. The combination according to claim 1, in which said ribs arecorrugated longitudinally of the strip.

3. The combination according to claim 1, in which said areas are concavetransversely of the strip.

4. In combination, a stack of laminations superimposed in face-to-facerelation said stack having a groove across the edges of the respectivelaminations, said groove having an arcuate bottom wall deeper along thecenter line of the groove than at the sides thereof and having sidewalls substantially perpendicular to a chord across the arc, and anelongated strip of banding material having a bottom surface conformingto and in tight frictional en gagement with said bottom Wall atlongitudinally spaced areas and having opposite side edges compressedagainst said side walls in said longitudinally spaced areas.

5. The combination of claim 4, in which the strip at said longitudinallyspaced areas is arcuate in cross section.

6. The combination of claim 5, in which the arcuate shape of saiddepressed longitudinally spaced areas provides increased areas ofcontact with the side walls of the groove.

7. In combination, a stack of laminations superimposed in face-to-facerelation, said stack having a groove across the edges of the respectivelaminations, said groove being generally rectangular in cross section,and an elongated strip of banding material positioned in said groove andhaving alternating transversely extending depressed areas and ribs onthe top surface thereof, the bottom surface of said strip in said areasconforming to and in tight frictional engagement with said bottom Wall,and the opposite side edges of said strip in said areas being compressedagainst said side walls, the strip in the space between said areas beinglongitudinally corrugated.

8. In combination, a stack of laminations superimposed in face-to-facerelation, said stack having a groove across the edges of the respectivelaminations, said groove being generally rectangular in cross section,and an elongated strip of banding material positioned in said groove andhaving alternating transversely extending depressed areas and ribs onthe top surface thereof, the bottom surface of said strip in said areaconforming to and in tight frictional engagement with said bottom Wall,and the opposite side edges of said strip in said area being compressedagainst said side Walls, said strip at said areas being thicker at theside edges of the strip than in the center portion of said strip.

9. In combination, a stack of laminations superimposed in face-to-facerelation, said stack having a groove across the edges of respectivelaminations, said groove being generally rectangular in cross section,and an elongated strip of banding material positioned in said groove andhaving alternating transversely extending depressed areas reduced on thetop surface thereof, the bottom surface of said strip in said areaconforming to and in tight trictional engagement with said bottom wall,and the opposite side edges of said strip in said areas being compressedagainst said side walls, said bottom wall of the groove and the bottomsurface of said strip being substantially flat and in engagement in saidareas, and the edge portions of the strip being thicker than the centerportion of said strip in said areas.

References Cited in the file of this patent UNITED STATES PATENTS2,574,417 Rowe Nov. 6, 1951 2,610,225 Korski Sept. 9, 1952 2,849,695Schaefer Aug. 26, 1958 FOREIGN PATENTS 723,521 Great Britain Apr. 16,1951

1. IN COMBINATION, A STACK OF LAMINATIONS SUPERIMPOSED IN FACE-TO-FACERELATION, SAID STACK HAVING A GROOVE ACROSS THE EDGES OF THE RESPECTIVELAMINATIONS, SAID GROOVE BEING GENERALLY RECTANGULAR IN CROSS SECTION,AND AN ELONGATED STRIP OF BANDING MATERIAL POSITIONED IN SAID GROOVE ANDHAVING ALTERNATING TRANSVERSELY EXTENDING DEPRESSED AREAS AND RIBS ONTHE TOP SURFACE THEREOF, THE BOTTOM SURFACE OF SAID STRIP IN SAID AREASCONFORMING TO AND IN TIGHT FRICTIONAL ENGAGEMENT WITH SAID BOTTOM WALL;AND THE OPPOSITE SIDE EDGES OF SAID STRIP IN SAID AREAS BEING COMPRESSEDAGAINST SAID SIDE WALLS.